Railway signaling system



Patented May 27, 1941 2,243,725 RAILWAY SIGNALING SYSTEM Leslie R. Allison, Forest Hills, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application February 21, 1940, Serial No. 320,146

3 Claims. (01. 246-38) My invention relates to a railway signaling interrupted energy, this means being arranged so system having track circuits employing coded that on initiation of code following operation of or periodically interrupted current. the relaythe means will not respond to such It has heretofore been proposed to provide operation of the relay until the contacts of the means operable in the event an insulated joint 5 relay have been moved between their picked-up separating two track sections is defective to and released positions a plurality of times. establish a lockout circuit to supply steady A further object of my invention is to provide uncoded energy to the section in the rear of code detecting means of the type described and the defective joint so that this energy will feed which is arranged to quickly detect when the over the defective joint and maintain the track code following relay ceases to respond to coded relay of the section in advance of the defective energy. joint constantly energized to thereby cause the Another object of my invention is to provide signal controlled by the track relay to display a coded railway signaling system which is arits most restrictive indication. ranged so that if a train enters a section in It has also been proposed heretofore to provide which the track relay is energized with steady a system of the type referred to and to arrange uncoded energy, the equipment will not operate the system so that after the contacts of the to cause a flash of the yellow or caution lamp track relay have been released for a time interval of the signal for such section. and code following operation of the contacts is Another object of my invention is to provide initiated, the lockou or steady energy supply an improved coded railway signaling system. circuit will not be established on the first move- Other objects of the invention and features ment of the track relay contacts to their picked of novelty will be apparent from the following up position. This arrangement was devised to description taken in connection with the accomprevent cascading action in the event an panying drawing. insulated joint separating two sections is defec- I shall describe three forms of apparatus tive and steady energy is supplied to the section embodying my invention, and shall then point in the rear, or if steady energy is sup plied to a out the novel features thereof in claims. track section to discontinue operation of a high- In the drawing: way crossing signal. Fig. 1 is a diagram of a railway signaling sys- In such a system. the lookout circuit for 3 tem employing the improved code detecting supplying steady energy to the adjacent section means provided bythis invention, in the rear of a defective joint is established Fig. 2 is a diagram of a railway signaling syson a. movement of the track relay contacts to term incorporating the improved non-cascading their picked up position subsequent to their first lockout circuit provided by this invention, and movement to such position, while the lockout Fig. 3 is a fragmentary diagrammatic view circuit is interrupted if the track relay continues showing a modification which may be employed to respond to coded energy. A system embodyin the system shown in Fig. 2. ing these characteristics is shown in an applica- Referring to Fig. 1 of the drawing, there is tion of Ralph R. Kemmerer, Serial No. 282,185, shown therein a stretch of'railway track having filed June 30, 1939, for Railway signaling system, 40 track rails l and 2 over which trafiic normally now U. S. Patent No. 2,215,904, granted Sept. moves in the direction indicated by the arrow. 24, 1940. The track rails of the track stretch are divided It is an object of my invention to provide a by insulated joints 3 into the customary successystem of the type described which will be nonsive track sections which are identified as IT, cascading in operation and which employs less HT, and HT. apparatus than the system heretofore known has a The particular track stretch shown in Fig. 1 required. is intended for use in a railway system employ- A further object of my invention is to provide ing steam for propulsion purposes, and while an improved railway signaling system incorpoalternating current is employed in the track cirrating a lookout circuit, the system being cuits, it should be understood that coded direct arranged so that it is non-cascading in operation. current may be employed if desired.

. Another object of my invention is to provide Each of the track sections has positioned at code detecting means adapted for use in a coded the entrance end thereof a wayside signal S signaling system to ascertain when a code folwhich indicates to an approaching train the lowing relay is responding to coded or periodically nature of the tra'ific conditions in the sections immediately ahead. The particular signal shown is of the well-known color light type having three lamps G, Y, and R. It should be understood, however, that my invention is not limited to the use of this type of signal, and that any other suitable type of signal may be employed if desired.

The rails of each of the track sections form a part of a track circuit to which coded alternating current signal control energy normally is continuously supplied through a track transformer TT, the secondary winding of which is connected with the rails at the exit end of the section. The connection of the transformer with the track rails includes the usual current limiting reactor 6. The energy supplied to the track circuits is derived from any suitable source and may 'be distributed throughout the track stretch by a transmission line, not shown. In the drawing the reference characters BX and CK designate terminals which are supplied from such source.

Each signal location has associated therewith a source of direct current, such as a primary or storage battery, not shown, the terminals ofwhich are designated Band C in the drawing.

The signaling system shown in Fig. 1 is of the three-indication variety and makes use of track circuit energy of two different codings. These codings are produced by code transmitters CT which interrupt the supply circuits of the track transformers a definite number of times a minute according to trafiic or other conditions ahead. In the form shown each code transmitter CT is provided with two circuit making and breaking contacts designated 75 and I8!) which are continuously actuated by a motor or other suitable mechanism at speeds such as to produce codes consisting of 75 and 180 energy pulses per minute, respectively, the energy pulses being separated by intervals of equal duration in which no energy is supplied.

Each of the track circuits includes a code following track relay TR having it operating winding connected through a resonant unit RU to the track rails of the track section adjacent the entrance end thereof. The resonant units RU include a transformer, a capacitor, and a reactor arranged and proportioned so as to freely .pass alternating current of the frequency employed in the signal control circuits, but so as not to pass current of a different frequency.

Each of the resonant units includes, in addition, a rectifier for rectifying the current supplied through the resonant unit to the winding of the track relay.

In the system shown in Fig. 1, energy of one or the other of the two previously described code frequencies, namely 15 or 18,8, is normally fed to the track circuits at all times. However, it may be desired to at times Supply steady uncoded energy to a track circuit to discontinue operation of a highway crossing signal, as explained in'the application of Ralph R. Kemmer identified above.

Similarly, where the track sections are long, it may be desired to divide a track section into two parts, and to provide means at the junction between the two parts to repeat to the rear portion the code supplied to the forward portion of the section. It may also be desired to employ back contact coding at the cut sections to prevent code distortion. This will result in the supply of steady uncoded energy to the rearward portion of the section when the forward portion of the section is occupied. One form of apparatus which may be employed at the cut sections to provide this back contact coding is shown in an application of Charles B. Shields and Herman G. Blosser, Serial No. 275,146, filed May 23, 1939, for Railway traffic controlling apparatus, now U. S. Patent No. 2,211,174, granted Aug. 13, 1940.

Each of the track relays has associated therewith auxiliary relays FSA and H which serve to determine when the contacts of the track relay TR are responding to .coded energy, and an auxiliary relay J which determines when the track .relay is responding to energy of the 18!] code frequency. The auxiliary relays FSA and H control the supply of energy to the track circuit of the adjacent track section in the rear, while the auxiliary relays H and J jointly control the signal for the associated track section.

The contacts i5 and I6 of the track relay IITR are :connected to terminal B of the local source of direct .current. Contact l6 when picked up engages a contact which is connected to one terminal of the winding of relay 1 iFSA, the other terminal of which is connected to terminal C of the source of current. A snubbing resistor 20 is connected across the terminals of the winding of the relay 1 IFSA to render the relay contacts slow in releasing.

Contact I! of relay TB is connected to one element of an electrolytic condenser HEC, while the other element of the condenser is connected to terminal C of the source of direct current and also to one terminal of the winding of relay l-IH, the other terminal of which is connected to-a contact which is engaged by contact 17 when contact I! is picked up. Contact I'! when released engages a contact which is connected to contact 22 of relay HFSA, while contact 22 when picked up engages a contact which is connected to terminal B of the source-0f direct current.

A snubbing resistor $23 is connected across the terminals of the winding of relay HH to render the relay contacts slow in releasing.

Contact l5 of track relay I-ITR controls the supply of current to the primary winding 25 of the decoding transformer l IDT. Contact l5 when picked up engages a contact which ,is connected to one end terminal of the transformer primary winding, and when released engages a contact which is connected to the other end terminal of the transformer primary windingwhilethe center terminal of the winding 25 is connected to terminal C of the local source of direct current.

The secondary winding 26 of the transformer 'HDT is connected .to resonant unit I IRUA which is connected to the terminals of the winding of relay HJ. The=resonant unit HRUA comprises a reactor and ,a capacitor arranged and proportioned to freely pass energy of the frequency supplied by the secondary winding "26 when the contacts of track relay H TR are responding to energy of the F code frequency, but so as not to pass a substantial amount of energy of the frequency present when the track relay contacts are 'responding'to coded energy of a different frequency, as, for example, the 15 code frequency. The resonant unit 'IIRUA includes :a rectifier which rectifies the current supplied to the winding of relay NJ.

The track transformer IfiTT has a primary winding 28, one terminal of which is connected to terminal CX of the source of signal control current, and the other terminal of which is connected to contact 29 of relay HFSA. Contact 29 when released engages a contact which is connected to contact 15 of the code transmitter 1 I'CT,'while contact 29 when picked up engages a contact which is connected to contact 33 of relay IIH.

Contact 30 when released engages a contact which is connected to contact I of the code transmitter, while contact 34] when picked up engages a contact which is connected to contact I80 of code transmitter II'CT.

The contacts F5 and I80 of code transmitter I I CT intermittently engage front contacts which are connected by wire to terminal BX of the source of signal control current.

The relay IIH has a contact 32 which is constantly connected to terminal 3 of the source of direct current, and which when released engages a contact which is connected to one terminal of the red or stop lamp R, the other terminal of which is connected to terminal C of the source of current.

Contact 32 when picked up engages a contact which is connected to contact 33 of relay I IJ. Contact 33 when released engages a contact which is connected to a terminal of the yellow or caution lamp Y, the other terminal of which is connected to terminal 0 of the source of current. Contact 33 when picked up engages a contact which is connected to one terminal of the green or clear lamp G, the other terminal of which is connected to terminal C of the source of current.

The equipment shown in Fig. 1 is shown in the condition which it assumes when the track stretch is vacant for at least one section in advance of section I'IT. At this time the equipment associated with section IZT operates to supply energy of the 180 code frequency to the transformer IITT so that energy of this code frequency is supplied to the rails of section HT, and thus to the winding of track relay IITR with the result that the contacts of the track relay I ITR are picked up and released at this code frequency.

During the picked up periods of the track relay contacts, contact I6 establishes the circuit to supply energy to the winding of relay IIFSA. The supply of current to this relay winding is interrupted during the released-periods of the track relay contacts, but the contacts of the relay I iFSA are slow enough in releasing to remain picked up during the intervals between the supply of impulses of energy to the relay winding.

As the contacts of relay IIFSA are picked up, contact 22 establishes connection from terminal B of the source of direct current to back point of contact I! of the track relay IITR. Accordingly, during the released periods of the track relay contacts, a circuit is established to charge the condenser IIEC, this circuit being traced from terminal B of the source of current throughcontact 22 of relay I IFSA, contact I! of relay IITR to one element of the condenser IIEC, the other element of which is connected to terminal C of the source of current. As a result of connection of the two elements of the condenser to the terminals of the source of current, a charge is built up between the condenser elements.

When contact I? of the track relay TB. is picked up, the circuit for charging the condenser is interrupted and a circuit is established to supply energy from the condenser to the winding of relay III-I. This circuit is traced from one of the condenser elements through contact ll of relay HTR to one terminal of the winding of relay IIH, the other terminal of which is connected to the other element of the condenser.

It will be seen, therefore, that when the contacts of the track relay II'TR are responding to coded energy, contact 22 of relay I I FSA is picked up so that during the released periods of the track relay contacts, a circuit is established to charge the condenser IIEC, while during the picked up periods of the track relay contacts, a circuit is established to supply energy from the condenser to the winding of relay I II-I. The condenser IIEC and the relay IIH are proportioned so that the impulses of energy supplied from the condenser to the relay winding are of such magnitude that the contacts of the relay will be picked up, and will remain picked up during the intervals between the supply of impulses of current to the relay winding, when the track relay IITR is responding to coded energy of either of the frequencies employed in the control of the signals. Accordingly, since the track relay I ITR is responding to coded signal control energy, the contacts of relays I IFSA and I IH are picked up.

As it is assumed that section I2T is not occupied at this time, energy of the 180 code frequency is supplied to the rails of section IllT. During the released periods of the track relay contact I5, energy is supplied to the lower portion of the primary winding 25 of the decoding transformer IiDT, while during the picked up periods of the contact I5 energy is supplied to the upper portion of the primary winding 25. As a result of the alternate energization of the two portions of the winding, energy is induced in the secondary winding 26, and since the track relay is responding to energy of 180 code fre-- quency, the frequency of the current induced in the transformer secondary winding 26 is such that it is freely passed by the resonant unit IIRUA, and sufficient energy is supplied tothe winding of relay IIJ to maintain the contact of the relay picked up.

As the contacts of relays IIJ and IIH are picked up, the circuit for supplying energy to the green lamp G of signal I IS is complete, and this lamp is lighted to indicate that there are at least two clear sections in advance of the signal I IS.

As the contacts of the relays IIFSA and IIH are picked up, the circuit for supplying energy of the 180 code frequency to the transformer IIITT is established. This circuit is traced from terminal BX of the source of signal control current through contact I80 of code transmitter IICT, front contact 30 of relay IIH, front contact 29 of relay I IFSA, and primary Winding to terminal CX of the source of signal control current.

Operation of equipment on passage of a train in normal direction of trafiic When a train moving from left to right enters section IIT, the wheels and axles of the leading vehicle shunt the track relay IITR' and the contacts of this relay thereafter remain in their released position. As contact I6 does not engage its front contact, no energy is supplied to the winding of relay IIFSA and the contacts of this relay thereupon become released. Likewise, as contact I! does not engage its front contact, impulses of energy are no longer supplied from the condenser IIEC to the relay IIH and the contacts of relay I IH become released, while as contact 22 of relay IIFSA is released, the circuit for supplying energy to the condenser I IE0 is interrupted.

On entrance of the train into the track stretch with resultant shunting of the track relay IITR, the relay contacts become released and contact I-'I- engages its back contact to establish the circuit for supp-lying energy to the condenser I IEC'. This circuit is complete as long asthe contact 22 of relay I i'FSA remains picked up, while because of the slow releasing characteristics of relay HFSA the contact 22 of the relay remains picked up for an appreciable time interval. subsequent to movement of the track relay contacts to their released position. Accordingly energy is supplied to the condenser IIEC for a period of time long enough to build up a charge of substantial value between the elements of the condenser I IEC'.

The characteristics of the condenser IIEC are such, however, that any charge built up between the condenser elements at the time the contacts of the track relay and of the relay IIFSA- become released will be quickly dissipated by leakage between the condenser elements so that on subsequent picking up of the track relay contacts little or no energy is supplied from the condensertothe winding of relay IIH. The characteristics of the condenser IiEC are such that the charge between the condenser elements is reduced to a low ineffective value in a shorter time than is required for a train to traverse a track section.

As the contacts of the track relay remain intheir released positions, no energy is induced in the secondary winding '26 of transformer IIDT, and hence no energy is supplied to the relay IIJ and the contact of that relay becomes released.

As a result of the release of the contact 32 of relay IIH, the circuit for illuminating the green lamp-G is interrupted and the circuit for lighting thered lamp R. is established.

On release of contact 29 of relay I'IFSA, or on release of contact 38 of relay III-I, the circuit traced above for supplying energy of the 180 code frequency to the transformer Ill'IT is interrupted, and a circuit is established to supply energy of the '75 code frequency to the transformer IliTT. This circuit includes contact T- of code transmitter- II'CT, back contact 29* of relay IIFSA, and winding 28-.

When the rear of the train vacatessection I'fl'l, the energy of '75 code frequency supplied to the rails of that section feeds to the track relay of the section, and the equipment associated therewith operates as hereinafter explained in detail to light the yellow or caution lamp Y of the associated signal, and to supply energy of the 180 code frequency to the section in the rear.

When the train enters section I2T, the track relay for that section is shunted, and the equipment associated therewith operates as described in detail in connection with section HT to condition the signal to display its red or stop indication, and to supply energy of the 75 code frequency to, the rails of section I IT.

As long as any portion of the train remains in section I IT, the track relay I-ITR is shunted, but when the rear of the train vacates the section IIT, the energy of '75 code frequency will feed to the track relay l-iTR and effect code following operation of the contacts thereof. On the first picked up period of the track relay contacts contact I6 engages its front point of contact and en ergy is supplied to the winding of relay I IFSA so that the contacts of this relay become pickedup.

On the first movement of the track relay contacts to their picked up positions a circuit is established by contact I! to supply current from the condenser IIEC to the winding of relay I IH,

but. at: this time little or no. charge is present between the condenser elements, and no energy, or too little energy, is supplied to the winding of relay III-I to effect picking up ofthe relay contacts.

On the. first released period of the track relay contacts following their first picked up period energy is supplied over back contact ll of the track relay to.-condenser I IEC since contact 22 of relay IIFSA isipicked up at this time.

Accordingly a. charge is established between the elements of the condenser IIEC so that on the next or second picked up period of the track relay contacts energy is supplied from the conr denser to the winding of relay I IE1 and the contacts of relay I-.I-H are picked up. As explained above, on subsequent picked up periods of the track relay contacts impulses of current are supplied from the condenser to the winding of relay III-I to maintain the contacts of relay III-I picked up.

On picking up of contact 29 of relay I IFSA the previously traced circuit for supplying energy of the 75 code frequency to the transformer IflTT is interrupted, but the supply of energy of this frequency is continued over the circuit which includes back contact 38 of relay III-i, and front contact 29 of relay IIFSA until contact 30 of relay III-I becomes picked up.

When the contacts of relays HFSA and HE are both picked up, the supply of energy of '75 code frequency to the transformer IGTT is interrupted, and the previously traced circuit for supplying energy of the code frequency to the transformer IIl'IT is established.

At this time as the track relay IITR is responding to energy of the '75 code frequency, the frequency of. the current induced in the secondary winding 26 of the transformer IIDT is such that too little current is passed by the resonant unit I IRUA to effectively energize the Windingof relay IIJ, and hence the contact of relay IIJ- remains released. As contact 32 of relay HE is picked up and contact 33 of relay IIJ is released, the circuit for illuminating the red lamp R is interrupted, and the circuit for lighting the yellow or caution lamp Y is established.

When the train has advanced far enough in the track stretch to vacate section IZT, the track relay for that section responds to energy of the '75 code frequency supplied thereto, while the equipment associated with that track relay operates, as described in detail above to supply energy of. the 180 codefrequency to the rails of section On this change in the frequency of the code supplied to the rails of section I'IT, the contacts of the relay IITR operate at a correspondingly more rapid rate, and the resonant unit IIRUA passes sufficient energy to effect picking up of the contact of, relay IIJ. As a. result of picking up. of the contact of relay IiJ, the yellow or caution lamp Y is extinguished, while the green or proceed lamp G is lighted, and the supply of energy of 180 code frequency to the section IOT is continued.

Operation of equipment when a train enters a section to which steady energy is supplied For purposes of illustration it will be assumed that. the. section in advance of section HT is occupied. and that as a result of such occupancy, steady uncoded. energy is supplied to. the relay IITR. As. pointed out above, this supply of steady energy might be for. the purpose of discontinuing operation of a highway crossing sig-' nal, not shown, or it may be incidental to the use of back contact coding apparatus at a cut section.

When steady energy is supplied to the track relay IITR, the contacts of relay IITR. are held picked up and contact I6 establishes the circuit to supply energy to the winding of relay IIFSA so that the contacts of relay IIFSA are maintained picked up.

As the track relay contacts are held in their picked up positions, contact I1 engages its front contact to establish the circuit from the condenser IIEC to the winding of relay IIT, but since the condenser is not periodically charged, no energy is available to energize the winding of relay I IH and the contacts of this relay are released.

As the contacts of relay I IH are released, contact 29 maintains the circuit for supplying energy of the 75 code frequency to the transformer Ill'IT, while contact 32 maintains the circuit for illuminating the red or stop lamp R of signal I IS.

If under these conditions a train enters section IIT, the track relay IITR will be shunted and its contacts will be released. On release of contact I6 the circuit for supplying energy to the winding of relay II FSA is interrupted, while on release of contact I! the circuit for charging the condenser IiEC is established, and is complete until contact 22 of relay IIFSA becomes released which occurs shortly after release of the track relay contacts.

However, as a result of release of contact E1 of the track relay IITR, the circuit for supplying energy to the winding of relay II H is interrupted, and continues to be interrupted until the track relay contacts are picked up, which does not occur until the track section is vacated. Accordingly, on release of the track relay contacts the relay I IH remains deenergized, and contact 32 maintains the circuit for illuminating the red or stop lamp R, while there is no possibility that the contact 32 of relay III-I will be momentarily picked up to cause a flash of the yellow or caution lamp Y.

As the train proceeds through the track stretch and the rear of the train vacates section IIT, steady uncoded energy will again be supplied to the rails of section IIT and the contacts of the track relay I I TR will again become picked up. On picking up of the track relay contact I6 energy is supplied to the winding of relay IIFSA. At this time the charge built up in the condenser IIEC will have been dissipated, and on picking up of contact I! of the'track relay no energy, or insuflicient energy, will be supplied from'the condenser. to the winding of relay. III-I to efiect picking up of the relay contacts. Accordingly the contacts of relay IiH will remain released and no flash of the yellow or cautio lamp Y occurs at this time.

From the foregoing it will be seen thatthe system shown in Fig. 1 is arranged so that the H relay is energized when and only when the code following track relay is responding to coded energy, and, furthermore, that when code following operation of the track relay is initiated, energy is not sup-plied to the winding of relay H until the track relay contacts have moved between their picked up and released positions a plurality of times. This prevents momentary energization of the H relay on release of the track relay contacts at a time when the track relay is steadily energized. This prevents a flash of the caution or yellow lamp Y at such times which would occur if the H relay were to be momentarily energized.

Construction of the system shown in Fig. 2 of the drawing In Fig. 2 of the drawing there is shown a diagram of a portion of a railway signaling system incorporating the improved code detecting means provided by this invention.

The'system shown in Fig. 2 of the drawing is particularly intended for use on a railroad employing electric current for propulsion purposes, and operates to provide a non-cascading lockout circuit, the system being arranged so that it requires less apparatus than the systems heretofore proposed have required.

As the railroad shown in Fig. 2 of the drawing employs electric current for propulsion purposes, impedance bonds 4 are provided to conduct propulsion current around the insulated joints 3 which divide the railsl and 2 into the track sections I5T, I 6T, I'IT, etc. In additiomas the railroad employs electric current for propulsion purposes, alternating current is employed in the track circuits for signal control purposes. This current is of any suitable frequency, such as cycles per second, and is distributed throughout the track stretch in any suitable manner, such as by a transmission line not shown.

Each of the track sections has a code following relay TR which is connected through a suitable resonant unit RU of the type employed in the system shown in Fig. 1 to the track rails of the track section adjacent the entrance end thereof.

The track relays each have associated therewith auxiliary relays'A, F, G, H and J which co- The signal system shown in Fig. 2 of the draw-- ing is the 'same as that shown in Fig. 1- with respect to features not specifically mentioned and the description thereof will not be repeated. The equipment of this system is shown in the condition which' it assumes when the track stretch is vacant for at least one block'in advance of section 1ST." At this timethe equipment associated with section HT is conditioned to supply energy of the code frequency to the rails of section I 6T, while the contacts of all of the auxiliary relays associated with the track relay IGTR are picked up. The winding of relay ISA is energized by current supplied over a holding circuit which is traced from terminal B of a local source of direct current through contact 40 of relay.I6G and winding of relay ISA to terminal 0 of the local source of direct current. A snubbing resistor. II is connected across the terminals of the winding I6A to render the relay contacts slow in release mg.

element of which is connected to one terminal of,

the winding of relay IGF and also to terminal C of the source of direct current.

Accordingly-during the released periods of the As the winding of relay ISA is energized, its contact 42 is picked up to establish connection track relay contact 44 energy is supplied to the condenser l SEC :to build up acharge between the elements thereof, while during the picked up periods of the contact 44 it engages a contact which is connected to the other terminal of the winding of relay IEF so that at these times impulses of energy are supplied from the condenser I-SEC to the winding of relay IBF. These impulses of energy .are of sufficient value to maintain the-contacts of the relay "IBF picked up. The relay IBF is of a type which is slow releasing so that its contacts remain picked up during the intervals between the supply of impulses of current thereto.

The winding of relay IBG isenergized by current supplied over a circuit which is traced from terminal B of the source of current through front contact of relay IGG, front contact 41 of relay IzBF, and winding of relay [6G to "terminal C of the source of current. As long as th contact 4-! is picked up a snubbing resistor 48 is connected across the terminals :of the winding of relay IGG and renders'the relay contacts slow in releasing.

Relay I SHisenergiZed by current supplied over the circuit which is traced from terminal B of the source of current through front contact '50 of relay 'IEH, front contact "5| of relay 16G, and winding of relay I'BI-I'to terminal C of the source of current. A snulob'ing -resistor 52 is connected across the winding of relay IBH to render the relay contacts slow in releasing.

During the picked up periods of track relay contact 53 it engages a contact which is con. nected to one end terminal of the "primary winding 54 of the decoding transformer iBDT. During the released periods of contact 53 it engages a contact which is connected to the other end terminal of the primary winding 54, while the center terminal of the primary winding is connected to contact 55 of relay 16H. As contact 56 is picked up at this time it en'gages a contact which is connected o terminal C of the source of direct current. Accordingly as a result of movement of contact 53 of relay lBTR'between its two positions, the end portions of the primary winding I42 are alternately energized, and current is induced in the secondary winding 51, while this current is supplied through the resonant unit l-BR'U-A to the winding of relay IBJ. The resonant unit IERUA includes a rectifier which 'rectifles v the current supplied to relay "SJ, and the current supplied thereto is suiiicient to maintain the contacts of the relay picked up.

As the contacts of relays IBF, 16G, and H are picked up, the circuit for supplying energy of the ISO code frequency to the transformer l'fiT'I is established, and is traced from terminal BX of the source of signal control current through contact I851 of code transmitter IECT, front contact '60 of relay IBH, front contact 5! of relay 16G, and front contact 5.2 of relay IBF to one terminal .of the .primary winding 64 of transformer |.5'I'I the other terminal of which is connected to terminal CX of the source .of-

signal control current. Accordingly energy of the 180 code frequency is supplied tov section 151, and the equipment associated at that section Will respond to this coded energy.

As the contacts of relays 16H and IBJ are picked up, the circuit for illuminating the green lamp G of signal HES is established and is traced from terminal Bof the source of current through front contact 65 of relay L6H, and front contact 6.! of relay NJ to one terminal of green lamp G,

the other terminal of which is connected to terminal "C of the source of current.

Normal operation of the equipment on passage of a train When a train moving in the normal direction of traffic, that is from left to right, enters the section IGT, it shunts the track relay IBTR and the contacts of that relay thereafter remain in their released position. As contact 44 does not periodically engage its front contact, energy is not supplied from the condenser IBEC' to the winding of relay 16F and the contacts of relay [6]? thereupon become released.

On release of the contacts of relay IBF, contact 41 interrupts the previously traced circuit for energizing the winding of relay IBG. In addition, the circuit for connecting the snubbing resistor 48 in parallel with the relay winding is interrupted, and, therefore, the contacts of relay IGG quickly become released.

On release of the contact 5| of relay ISG, the circuit for energizing the winding of relay IGH is interrupted, and the contacts of that relay thereupon become released so that contact 56 of relay IBI-I interrupts the circuit of the primary winding 54 of transformer IBDT.

In addition, on release of contact 43 of relay IGG the circuit for energizing the Winding of relay IBA is interrupted and the contacts of that relay become released.

As the contacts of the track relay IBTR, no longer continue to respond to coded energy and as the circuit of the transformer primary winding 54 is interrupted by contact 55 of relay H, no current is induced in secondary winding 51 of transformer EDT, and hence current is not supplied through the resonant unit IBRUA to energize the winding of relay I6J and the contact of that relay becomes released.

As a result of the release of contact of relay l fiH, the circuit for illuminating the green lamp G of signal [GS is interrupted,.whi1e the circuit for illuminating the red lamp R is established and includes badk contact 65 of relay IBH.

On release of contact 62 of relay IBF the pre- Viously traced circuit for supplying energy of the I30 code frequency to transformer I5TT is interrupted, While on release of contact 6| of relay IGG the circuit for supplying energy of the 15 code frequency to the transformer IE'I'I is established.

The circuit for supplying energy of 15 code frequency to the transformer I5I'I' is traced from terminal BX of the source of signal control energy through back contact 6| of relay 16G, back contact 62 of relay ISF, and contact 15 of code transmitter IEC'I to' a terminal of the winding 64 of transformer IE'I'I, the other terminal of which is connected to terminal CX of the source of signal control energy.

As the train continues through the track stretch and. enters section I 1T, the track relay of that section is shunted, and the equipment associated therewith operates in the manner describedimdetail in connection with section I6T so that the supply of energy to transformer I 6TT is changed from the H30 code frequency to the L5 code frequency.

f As long as any portion of the train remains in section -l-6T, the track relay IETR continues to be shunted, but when the rear of the train vacatesseotion I ST, the energy of 15 code frequency supplied through the transformer l-6TT will feed to the track relay and effect code following operation of the relay contacts. On the first movement'of the track relay contacts to their picked up position, contact 53 completes the pick-up circuit for energizing the winding of relay IBA. The circuit for energizing this relay winding includes front contact 53 of track relay IGTR, back contact 69 of relay I BF, and back contact 40 of relay IBG to one terminal of the winding of relay [6A, the other terminal of which is connected to terminal C of the source of current. As a result of energization of the winding of relay ISA, the contact 42 of this relay becomes picked up so that on the next or first released period of the track relay, contact 44 completes the circuit for supplying energy to the condenser IGEC. Accordingly a charge is established on the condenser IBEC at this time.

On the next or second picked up period of the track relay contacts, contact 44 engages its front point of contact with the result that an impulse of energy is supplied from the condenser "SEC to the winding of relay IGF to effect picking up of the contacts of this relay.

On picking up of the contacts of relay I BF contact 69 is picked up and interrupts the previously traced circuit for supplying energy to the winding of relay ISA, while contact 4? of relay IGF establishes a circuit to supply energy to the winding of relay [6G on the next or second released period of the track relay contacts.

On picking up of contact 69 of relay IBF the circuit for supplying energy to the winding of relay ISA is interrupted, but a stick circuit is established to supply energy to the Winding of relay ISF as long as the contacts of relay 16G remain released. This stick circuit is traced from terminal B of the source of current through front contact 53 of the track relay IB'I'R, front contact 69 of relay I51, and back contact H3 of relay IBG to one terminal of the winding of relay IBF, the other terminal of which is connected to terminal C of the source of current.

The energy supplied over the above traced stick circuit to the Winding of relay 16F insures that the contacts of relay I61 will. be held picked up even if the contacts of relay 16A should become released so that energy is not supplied to the condenser |6EC to charge it during the released period of the track relay contacts.

On the next or second released period of the track relay contacts energy is supplied to the winding of relay IEG over the pickup circuit which is traced from terminal B of the source of current through back contact 53 of relay IBTR, back contact 45 of relay I 6G, front contact 41 of relay WP, and winding of relay I 66 to terminal C of the source of current As soon as the winding of relay |G is energized, the relay contacts become picked up and contact 45 interrupts the just traced pick-up circuit for supplying pick-up energy to the winding of relay IBG, while the stick circuit traced in detail above is established to maintain the winding of relay IBG energized as long as contact 4! of relay EEF remains picked up.

On picking up of the contacts of relay IEG contact 40 establishes the previously traced holding circuit for supplying energy to the Winding of relay IEA. The circuit for supplying pick-up energy to the winding of relay IBA was interrupted When the contact 69 of relay 15F became picked up, which occurred on the second picked up period of the track relay contacts, while the holding circuit for supplying energy to the winding of relay 16A is established on picking up of contact 40 of relay 15G which occurs on the second released period of the track relay contacts. The contacts of the relay [5A are rendered slow in releasing by the snubbing resistor 4|, and the relay and its resistor are arranged-and proportioned so that the contact 42 of this relay will remain picked up throughout the interval between the time at which contact 59 of relay I6F becomes picked up and the time at which contact 40 of relay ISG becomes picked up. Accordingly the contacts of relay 56A will be maintained picked up continuously.

On the next or third picked up period of the track relay contacts, energy is suppliedto the winding of relay |6H over the circuit which istraced from terminal B of the source of current through front contact 53 of relay IGTR, back contact 50 of relay 15H, front contact 5| of relay MG, and winding of relay IBH to terminal C of the source of current. On picking up of the contacts of relay IBH, contact 50 interrupts the above traced circuit, while this contact establishes the stick circuit to maintain the relay winding energized as long as contact iii of relay ISG is maintained picked up.

It will be seen, therefore, that on the third picked up period of the track relay contacts the relays IGA, 16F, IGG, and SH are all energized. It will be seen also that the relays IBA, IBG, and [6H are thereafter maintained energized by current supplied over stick circuits, and not by current supplied over circuits including contacts of the track relay IBTR. The relay IBF, however, continues to be supplied with current impulses from the condenser IGEC, while the condenser is recharged by current supplied over the back contact of track relay contact 44.

It will be seen also that when code following operation of the contacts of the track relay IBTR, has continued long enough to efiect picking up of the contacts of the relay IfiH, contact 56 of relay IBH establishes connection from the'center ter minal of the primary winding of transformer IliDT to terminal '0 of the local source of direct current. Accordingly on subsequent movement of the track relay contact 53 between its picked up and released positions the two end portions of the primary winding 54 of transformer IGDT are alternately energized and current is induced in the secondary winding 5'8.

In addition at this time the connections through which energy was supplied through track relay contact 53 to the windings of relays IGA, EEG, and NH are interrupted so that after the contact 56 of relay iEH completes the circuit of the trans former primary winding the track relay contact 53 serves only to control the supply of energy to the transformer primary Winding.

At this time as the windings of the relays ISA, PEG, and 5B are disconnected from the circuits associated with the track relay contact 53, the release time and operating characteristics of the relays are not affected by the transformer primary winding 55, as would be the case if the relay windings continued to be connected to the circuits through which energy is supplied to the transformer primary winding.

As the track relay EETR is responding to energy of the '15 code frequency, the frequency of the current induced in the secondary winding 51 of decoding transformer IGDT is not-such as to effect picking up of the contacts of relay IGJ.

It will be seen also that on picking up of contact 62 of relay ISF, which occurred on the second picked up period of the track relay contacts, the circuit for supplying steady uncoded energy to the transformer ISTT was established, and is traced from terminal BX of the source of current through back contact 6! of relay IEG, and front contact 62 of relay H515 to a terminal of the winding 65, the other terminal of which is connected to terminal CX of the source of signal control energy.

The steady energy supply circuit is interrupted on picking up of contact SI of relay IGG, which occurs on the second released period of the track relay contacts, While on picking up of contact 6! of relay ISG the circuit for supplying energy of the l 80 code frequency to the transformer I'IT is partially completed, and becomes complete when the contact 69 of relay I5H becomes picked On continued movement of the train through the track stretch so that it clears section HT, the

equipment associated with the track relay for that section operates in the manner described in detail above in connection with section IGT, and energy of the 180 code frequency is supplied to the section l-GT. On the resultant more rapid operation of the contacts of the relay IGTR sufiicient energy is passed by the resonant unit IGRUA to effect picking up of the contact of relay IBJ to thereby extinguish the yellow lamp Y of signal IBS and establish a circuit to illuminate the green lamp G of the signal.

The normal operation of the equipment shown in Fig. 2 on passage of a train having been described, its operation in the event an insulated joint breaks down as a result of passage of a train will now be considered.

Operation of equipment in the event an insulated joint breaks down as a result of passage of a train If a train traveling in the normal direction of trafiic enters the track section lfiT, and an insulated joint 3 separating sections IBT and HST breaks down as a result of the passage of the train, the track relay IBTR will be shunted, as explained in detail above, and the auxiliary relays associated therewith will be deenergized, while the signal lamp R of the signal |6S will be lighted, and energy of the 75 code frequency will be supplied to the transformer l5TT.

As long as any portion of the train remains in section I5T, the track relay of that section will be shunted, but when the rear of the train clears section l5T, the coded energy supplied to the track rails of that track section will feed to the track relay for section l5T and the equipment associated therewith will be conditioned to cause the yellow lamp of the signal therefor to be lighted, and to supply coded energy of the I86 coded frequency to the adjacent section in the rear.

In electrified territory, because of the wellknown operation of the impedance bonds 4, breaking down of one insulated joint has the same effect as breaking down of both insulated joints in steam propulsion territory, and permits the impulses of signal control current supplied to the section in the rear of the defective joint to feed to the track relay of the section in advance of the defective joint.

Because of the defective joint 3, therefore,

coded energy supplied to the rails of section 1ST will feed over the defective joint, but because of the shunting action on the wheels and axles of the train, insufficient energy will be supplied to the track relay IG'IR to effect code following operation thereof until the train has advanced far enough in the track stretch for the rear of the train to be located a substantial distance in advance of the track relay 1 6TB.

When a train has advanced this far, the contacts of the track relay ISTR will be picked up by an impulse of energy feeding over the defective joint from section I5T.

On the first picked up period of the track relay contacts, energy is supplied to the winding of relay 15A over the circuit which is traced from terminal B of the source of current through front contact 53 of the track relay IGTR, back contact 69 of relay IGF, back contact 40 of relay IEG, and winding of relay ISA to terminal Cof the source of current.

As a result of the supply of energy to the winding of relay ISA, contact 42 of this relay becomes picked up so that on the first released period of the track relay contacts following their first picked up period, energy is supplied over contact 44 of the track relay to charge the condenser lfiEC. As a result, on the next or second picked up period of the track relay contacts, energy is supplied from the condenser SEC to the winding of relay 16F and effects picking .up of the contacts of this relay.

On picking up of contact 62 of relay lGF the steady energy or lockout circuit for supplying steady uncoded energy to the transformer IETT is established, and is traced from terminal BX of the source of signal control current through back contact 62 of relay 16G, and front contact 62 of relay IBF to one terminal of the winding 64 of .transformer I5TT, the other terminal of which is connected to terminal CX of the source of signal control energy.

As a result of the supply of steady uncoded energy to the transformer IETT, steady energy is fed to the track rails of section I5T and feeds therefrom over the defective insulated joint 3 to maintain the contacts of the track relay IB'IR constantly picked up.

As the contacts of relay IBTR are constantly picked up, and as the contacts of relay 16F are picked up while the contacts of relay IGG are released, a holding circuit is complete to supply energy to the winding of relay i615 to maintain the winding of that relay energized. This holding circuit is traced from terminal B of the source of current through front contact 53 of relay IGTR, front contact 69 of relay I 6F, and

back contact 19 of relay 16G to one terminal of the winding of relay ISF, the other terminal of which is connected to terminal C of the source of current. As the winding of relay "FF is constantly energized, the contacts of the relay are maintained picked up and contact 62 maintains the steady energy or lockout circuit to supply steady uncoded energy to the transformer ISTT.

From the foregoing it will be seen that if an insulated joint breaks down as a result of passage of a train, then coded energy supplied to the section in the rear of the defective joint will feed over the joint and operate the track relay or" the section in advance of the defective joint. As a result of such operation of the track'relay by current feeding over the defective joint, the steady energy or lockout circuit will be established on the second picked up period of the contacts of the track relay of the section in advance of the defective joint, while as a result of the supply of steady energy, the contacts of the track relay for the section in advance of the defective joint will be held picked up and the relay I6F will be continuously energized and will maintain the steady energy or lockout circuit.

At this time the relay [6H is deenergized and its contact 65 is released to establish the circuit for illuminating the red or stop lamp R of the signal I68.

As the train proceeds through the track stretch and enters section IIT, the track relay for that section is shunted, and the signal for the section is conditioned to display its red orv stop indication, while current of the I code frequency is supplied to the transformer IGTT. When the rear of the train clears section IGT, the impulses of energy supplied by the transformer IETT feed to the track relay IGTR, but at this time the intervals between impulses of energy supplied by the transformer IETT are filled by the steady energy feeding over the defective insulated joint from section I5T with the result that the contacts of the track relay IB'IR are maintained steadily picked up. Accordingly relay ISF continues to be energized, while the contacts of relay IBH remain released and condition the signal His to display its red or stop indication.

The same condition continues when the train advances far enough to clear section I'IT, in which event the track relay for the section IIT conditions the signal associated therewith to 'display its yellow or cautionindication, while current of the I80 code frequency is supplied to the 'rails of section IBT. At this time since steady energy feeds over the defective insulated joint from section I5T, the contacts of the track relay IBTR are steadily picked up and no change occurs in the aspect of the signal IGS.

It will be seen that when the lockout-circuit is established and the contacts of relay IGF are picked up, contact 69 of relay ItF interrupts the circuit for energizing the winding of relay I6A, and the contacts of this relay thereupon become released. This is advantageous where the relay ISA is employed to control an interlocking relay for I controlling a highway crossing signal. Where such control is employed, the relay IGA when energized establishes a circuit to supply energy to the winding of the interlocking relay. This circuit is interrupted when the contacts of the relay ISA are released which is the condition when the lockout circuit is established.

The operation of the equipment shown in Fig. 2 if an insulated joint breaks down as a result of passage of a-train having been described, the operation of the equipment if an insulated joint breaks down while the track stretch is vacant will now be considered.

Operation of the equipment if an insulated joint breaks down when the track stretch; is vacant For purposes of illustration it will be assumed that the track stretch is vacant and that energy of the I88 code frequency is being supplied to the rails of section IST. As a result, all of the auxiliary relays associated with track relay IBTR are energized, while the signal I 68 will be conditioned to display its green or proceed indication, and energy of the I80 code frequency is supplied to the rails of section I5T.

When the insulated joint 3 separating sections I5T and I6T becomes defective, impulses of energy supplied to the rails of section I 5T feed over the defective joint and energize the track relay IGTR. g

If at the time the joint 3 becomes defective the impulses of code supplied to the section I5T are out of step with those supplied to the section IBT, the impulses of code supplied to section I5T will fill in the off periods in the code supplied to section IBT with the result that the contacts of track relay I BTR will be maintained picked up all or substantially all of the time.

If at the time the insulated joint separating sections I5T and IBT becomes defective the impulses of code supplied to the two sections are substantially in step with each other they will soon become out of step. This will be true because the code transmitters which create the code for the two sections are driven by electric motors and these motors will not operate 'at exactly the same speed. vAccordinglyif the track relay contacts are not heldv picked up for an abnormally large proportion of the time asla result of the unusually high value of current supplied to the relay winding. when the code impulses are substantially in step with each other, the track relay contactsiwill soon be held picked up an abnormally large portion of the time because of the increase in the time during which energy is supplied to the track relay winding when the two codes get out of step. r

In consequence of the lengthened picked up periods of the track relay contacts, too little or no. current is supplied to charge the condenser IBEC with the result that little or no current is available to energize the winding of relay IGF.

As a result, the contacts of relay IBF become released, and on release of contact 41 of therelay, the circuit for energizing the winding of relay I6G is interrupted, While on release of contact 62 of the relay IBF the circuit for supplying energy of the I code frequency to the transformer I 5TT is interrupted.

On release of contact 47 of relay IGF the circuit for energizing the winding of relay I 6G and for connecting the snubbing resistor 48 across the terminals of the winding of relay ISG is interrupted, and the contacts of relay IBG quickly become released.

On release of contact 5i of relay IfiG the circuit for energizing the winding of relay I SE is interrupted, while on release of contact 40 of relay I 6G the circuit for energizing the winding of relay IGA is interrupted. r

In addition on release of contact 6| of relay I 6G the circuit for supplying energy of the I5 code frequency to the rails of section I 5T is complate and current of this code frequency is supplied to that section. r

The energy of I5 code frequency suppliedto section I5T feeds over the defective joint 3 to the track relay IBTR. and combines with the energy of I80 code'frequency supplied to the rails of section IGT by the transformer IGTT with the result that the contacts of the track relay I STR will remain picked up and energy will be supplied to the winding of relay IBA to cause the contact 42 of that relayto be picked up. The circuit for supplying energy to the winding of relay ISA is traced from terminal B of the source of current through front contact 53 of the track relay IB'IR, back contact 69 of relay I BE, back contact 40 of relay IEG, and winding of relay IBA to terminal C of the source of current.

As a result of the supply of energy of two different code frequencies to the rails of section IBT, that is, energy of I 89 code frequency supplied through the transformer IGT'I, and energy of the code frequency feeding over the defective joint from section I5T, a time will soon come'when a relatively long oil interval will occur in the code, and the contacts of the track relay IB'IR; will be released for a substantial period of time so that contact 44- will engage its back contact long enough for a substantial charge to be built up between the elements of the condenser IGEC.

The contacts of the track relay will. soon thereafter become picked up again. and energy will be supplied from the condenser IGEC to the winding of relay IBF to effect picking up of the contacts of relay IfiF. As soon as the contacts of relay IEF are picked up, a stick circuit is established to maintain the relay winding energized,

\this stick circuit including front contact 53 of relayIB'I'R, front contact 69 of relay IBF, back contact 10 of relay 16G, and winding of relay 16F toterminal C of the source of current.

As a result of picking up of the contacts of relay, IBF, contact 62 is picked-up and establishes the lockout,or steady energy supply'circuit to supply steady uncoded energy to thetransformer ISTI. This steady energy feeding over the defective joint 3 to the track relay lE'I'R willmaintain the track relay contacts picked up with the result that the holding circuit forthe winding of relay IBF will be maintained and relay 16F will operate to maintain the lookout circuit.

As contact69 of relay l6F is picked up at this time, the previously traced circuit for energizing the winding of relay ISA is interrupted and the contact 42 of this relay becomes released, but

the relay IBF is maintained energized 'by current supplied over the stick circuit traced above.

At this time the winding of relay 16H is deenergized and the contact 65 of this relay remains released to maintain the circuit for lighting the red or stop lamp R of the signal its.

Operation of the equipment in the event the lockout circuit is interrupted The system provided by this invention is arranged so that if while the lockout circuit is established it is improperly interrupted for any reason, it will be automatically restored.

If the lockout circuit is temporarily interrupted for any reason, as for example shorting of. the

similar condition results if one of the wires connecting the track relay [6TH with the rails of section [ST is temporarily disconnected or shortcircuited at a time when the lockout is metfect.

On interruption of the supply of current to the rails of section I5'I' the track relay l.6TR..will. respond to coded energy supplied by the transformer IBTT.

On the first oil period in the code supplied by the transformer IGTT following the interruption of the lookout circuit, the track relay contacts become released and energy is supplie'dto the Winding of relay [5G over the circuit which is traced from terminal B of thesource of current through back, contact 53 of relay 'IG IR, back contact of relay [6G, and front contact fl'l-of relay IBF to one terminal of the winding of relay [6G, the other terminal. of which is connectedto terminal C of thesource of current. H

As a result of ener'gi'zation of the winding of relay IGG, the contacts of the relay are picked up and the circuit is established to supply current to the winding of relay I'BA, while, in addition, the stick circuit for supplying energy to the winding of relay IBF is interrupted, and the stick circuit for maintaining the winding of relay IGG energized is established.

Also, on picking up of the contacts of relay IBG, contact 6| interrupts the lookout circuit, while contact 5| ofthe relay establishes a circuit to supply energy to the winding of relay [6H on the next picked up period of the track relay contacts.

On picking up of contact 40 of relay l'BG energy is supplied to the winding of. relay [6A and the contact of this relay becomes picked up. On picking up of contact 42 of relay [6A, the contact 44 of relay IGTR being in its released position energy is supplied to the condenser IEEC, but the length of time during which energy is supplied to the condenser before the contacts of the track relay become picked up again is relatively brief and the condenser may be only partially. charged.

On the next picked up period of the track relay contacts energy is supplied from the condenser IGEC to the winding of relay 16F, but because of the low value of the charge on the condenser IGEC, insuflicient energy may be supplied to the winding of relay 16F to maintain the contacts of relay I6F'picked up until the next impulse of current is supplied to the relay winding and the contacts of relay 16F may become released during the next 0 interval in code.

On the first pickedup period of the track relay contacts, that is, the period under consideration, energy is supplied to the winding of relay [8H over the circuit which is traced from terminal B of the source of current through front contact 53' of relay IGTR, back contact 50 of relay lBH, front contact 5! of relay 5G, and winding of relay IBH to terminal C of the source of current.

On picking up of the contacts of relay 16H contact 50 establishes the stick circuit for the relay winding, while contact 60 of the relay completes the circuit .for supplying energy of the Hillv code frequency to the wire leading to the track transformer I5TT. Since it is assumed that the circuit for supplying energy to the transformer I ST]? is interrupted, this energy will not reach the transformer.

If the contacts of relay IBF remain picked up during the second off period in the code, the circuits for energizing the windings of the relays ISA, IGG, and IEH will be maintained, while the winding of relay HiF'will be supplied with impulses'of energy during subsequent picked up periods of the track relay contacts, and the contacts of all the auxiliary relays will be maintained picked up as long as the track relay continues to respond to energy supplied by transformer IGTT.

As pointed out above, the contacts of relay (SF-may become released during the second 0 interval in the code, and if they do, contact62 of relay IBF will interrupt the circuit for supplying jen'ergy of the I code frequency.

If thecont'act's of relay [6F become released at this time, the contacts of the relays I'6A, lBG, and NH will become released, while these relays and. relay 16F will be energized serially if the track relay ISTR continues to respond to coded energy, and these relays will thereafter remain energized as long as normal code following operation of the track relaycontinues.

If the supply of energy to the transformer lS'IT is now restored, the coded energy feeding over the defective insulated joint from section IT to the track relay IGTR will cause the contacts of the track relay toremain picked up for an abnormally large portion of the time, as explained above, with the result that insufiicient energy is supplied to the condenser IGEC to energize the relay IBF. The contacts of the relay 56F, therefore, will become released effecting release of the contacts of the auxiliary relays associated therewith, while relay I6F will subsequently become energized, and its contacts will be picked up to establish the lockout" circuit as explained above.

Modification shown in Fig. 3 of the drawing In Fig. 3 of the drawing there is shown a modified arrangement which I may incorporate in the system shown in Fig. 2. In the modification shown in Fig. 3 the relay IGFA, which takes the place of the relay [6F employed in the system shown in Fig. 2, is provided with two windings instead of the one winding with which the relay l 6F is provided.

The relay IEFA has a winding 15 to which energy is supplied from the condenser IGEC, and a winding 76 to which energy is supplied through the stick circuit for the relay. A snubbing resistor H is shunted across the winding 15 of the relay EBFA to render the relay contacts slow in releasing.

The wire leading from one element of the condenser ltEC is connected to thewinding 15 of the relay lSFA and also to terminal 0 of the source of current, while the wire leading from front contact 56 of the track relay lfiTR. is connected to the other terminal of the winding 15. Accordingly, when the contacts of the track relay IBTR are responding to coded energy, current impulses are supplied from the condenser I SEC to the winding 75 to maintain the contacts of the relay 1 EFA picked up.

The wire leading from back contact of relay IBG is connected to one terminal of the winding of relay IEFA, while the other terminal of this winding is connected to terminal C of the source of current. As a result, when the contacts of the track relay [6TB are picked up and the contacts of relay ltG are released, the stick circuit for maintaining the contacts of relay IGFA picked up is established and this circuit serves to energize the winding 76.

The operation of the system shownin Fig. 3 is substantially the same as that shown in Fig. 2 and a detailed description of the operation thereof is unnecessary.

Operation of the system shown in Fig. 2 of the drawing on the supply of steady energy to a rack circuit In the system shown in Fig. 2 of the drawing steady energy may be supplied to the rails of section lBT as a resultof establishment of the lockou circuit controlled by the track relay of the adjacent section in advance. Steady energy may also be supplied to the rails of a section similar to section IBT to discontinue operation of a highway crossing signal, not shown, as explained in detail in the application of Ralph R. Kemmerer identified above, or. steady energy may be supplied to a track relay as a result of operation of back contact coding facilities.

For purposes of illustration it will be assumed that an insulated joint 3 separating sections [ST and HT breaks down as a result of passage of a train moving in the normal direction of traffic, and that the equipment associated vnth section H'I' operates to establish the lockout circuit to supply steady uncoded energy to the rails of section IBT.

As explained above in connection with the equipment associated with section l6T, when a train enters a section, the equipment associated with that section is conditioned to supply energy of the 15 code frequency to the track'rails of the adjacent section in the rear, but the impulses of energy of this code frequency do not feed to the track relay of such section in the rear until the rear of the train has cleared that section.

Accordingly, when the train moving in the normal direction of trafiic enters section HT, impulses of energy of the 75 code frequency are supplied to the track transformer IGTT, but do not reach the track relay I BTR until the rear of the train vacates section IGT. Thereafter there is a short time interval before the train will have advanced far enough in the section HT for the contacts of the track relay for that section to be picked up by impulses of current feeding over the defective joint from section IBT. In this interval code following operation of the track relay IETR will occur and the re- 'lays ISA, I6F, IEG, and I6H will be serially energized in the manner explained in detail alcove.

When the train has advanced far enough in section HT for the track relay of that section to be energized by current feeding over the defective insulated joint, the equipment associated with the track relay for section HT will operate to establish the lookout or steady energy supply circuit, and steady energy will be su lied to the rails of track section IBT, and thereafter the contacts of relay IGTR will be maintained constantly picked up.

As a result of the supply of steady energy to the track relay IBTR at a time when the relays ISA, IGF, IGG, and SH are all energized, the contact 44 of relay IGTR will not periodically engage its back contact to eifect the supply of energy to the condenser EC, and hence the charge on this condenser will not be periodically restored and energy will not be available to en ergize the winding of relay "3F.

As a result, the contacts of relay IGF will become released, and on opening of contact 47 thereof the circuit for energizing the winding of relay 16G will be interrupted to thereby cause the contacts of that relay to become released. As a result of the release of the contacts of relay ISG, the circuit for energizing relay iEH is interrupted, while contact 49 completes the circuit to energize relay IBA, which circuit is coinplete at this time since contact 69 of relay I6F is released and contact 53 of the track relay I6TR is picked up.

As a result of the release of contact 52 of re lay I6F and contact 6| of relay EEG, the circuit for supplying energy of the 15 code frequency to the track transformer I5TT is complete, and energy of this frequency is therefore supplied to the rails of section 1ST.

At this time as the contacts of relay IiiA are picked up, a contact of this relay may be employed to establish a circuit to energize the winding of an interlocking relay, not shown, which may control a highway crossing signal, not shown.

Inaddition, as the contact 42 of relay IBA is picked up, the equipment is in condition to quickly respond to code following operation of the track relay lEIR, such as might occur when the train clears the section in advance of sec-- tion "ST and the supply of steady energyto the rails of section EST is discontinued where the steady energy was supplied to discontinue operation of a highway crossing signal.

Under such circumstances, on the first released period of the track relay contacts following the period in which they were constantly picked up, energy is supplied to charge the condenser IEEC, and on the first picked up period of the track relay contacts, energy is supplied H ing is arranged to provide the lockout or steady energy circuit to supply steady uncoded energy to the section in the rear of a defective insulated joint, while the system also operates so that if steady energy is supplied to a section by means other than the lockout circuit controlled by the track relay of that section, the equipment for that section will not operate to repeat the supply of steady energy to the section in the rear thereof, but will supply coded energy to that section.

This prevents any cascading action and makes it unnecessary to employ special cut section facilities to accomplish this purpose. It also makes it possible to employ steady uncoded energy for the purpose of discontinuing operation of highway crossing signals Where such is desired.

From the foregoing it will be seen that this invention provides means including a relay which is energized only after a plurality of movements of the code following track relay contacts between their two positions.

It will be seen also that this invention pro- Vides a signaling system incorporating this improved code detecting means and arranged to prevent a flash of the yellow or caution lamp when a train enters a section to which steady improved code detecting uncoded energy is supplied, and furthermore I what I of track rails divided by insulated joints into suc- V cessive track sections including a forward and a rearward section, means governed by traffic conditions in advance of the forward section for at times supplying periodically interrupted energy and at other times supplying steady energy to the rails of said forward section, a code following track relay having a winding receiving energy from the rails of said forward section, a first, a second and a third auxiliary relay andcan energy storage device associated with said track relay, a, circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a front contact of the first auxiliary relay and a back contact of the track relay for supplying current to the energy storage device, a circuit including a front contact of the track relay for supplying current from the energy storage device to a winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay and a back contact of the third auxiliary relay for also supplying energy to a winding of the second auxiliary relay, a circuit including a back contact of the track relay and a front contact of the second auxiliary relay for supplying energy to the winding of the third auxiliary relay, a circuit operative when the contacts of both the second and the third auxiliary relays are released to supply periodically interrupted energy to the rails of said rearward section, a circuit including a front contact of the second auxiliary relay and a back contact of the third auxiliary relay for supplying steady energy to the rails of said rearward section, and a circuit established on continued code following operation of said track relay subsequent to establishment of said steady energy supply circuit to supply periodically interrupted energy to the rails of said rearward section.

2. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into successive track sections including a forward and a rearward section, means governed by traffic conditions in advance of the forward section for at times supplying periodically interrupted energy and at other times supplying steady energy to the track relay having a winding receiving energy from the rails of said forward section, a first, a

second and athird auxiliary relay and an energy storage device associated with said track relay, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a front contact of the first auxiliary relay and a back contact of the track relay for supplying current to the energy storage device, a circuit including a front contact of the track relay for supplying current from the energy storage device to a winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay and a back contact of the third auxiliary relay for also supplying energy to a winding of the second auxiliary relay, a circuit including a back contact of the track relay and a front contact of the second auxiliary relay forsupplying energy to the winding of the third auxiliary relay, circuits operative when the contacts of both the second and the third auxiliary relays are picked up or when the contacts of both relays are released to supply periodically interrupted energy to the rails of said rearward section, and a circuit including a front contact of the second auxiliary relay and a back contact of the third auxiliary relay for supplying steady energy to the rails of said rearward section.

3-1In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into successive track sections including a forward and a rearward section, means governed by traffic conditions in advance of the forward section for at times supplying periodically interrupted energy and at other times supplying steady energy tothe rails of said forward section. a code following track relay having a winding receiving energy from the rails of said forward section, a first, a second, a third, and a fourth auxiliary relay and an energy storage device associated. with said track relay, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a front contact of the first auxiliary relay and a back contact of the track relay for supplying current to the energy storage device, a circuit including a front contact of the track relay for supplying current from the energy storage device to a winding of the second auxiliary relay, a circuit including front contacts of the track relay and of the second auxiliary relay and a back contact of the third auxiliary relay for also supplying energy to a winding of the second auxiliary relay, a circuit including a back contact of the track relay and a front contact of the second auxiliary relay for supplying energy to the winding of the third auxiliary relay, a circuit operative when the contacts of both the second and the third auxiliary relays are released to supply periodically interrupted energy to the rails of said rearward section, a circuit including a front contact of the second auxiliary relay and a back contact of the third auxiliary relay for supplying steady energy to the rails of said rearward section, a circuit including front contacts of the track relay and of the third auxiliary relay for supplying energy to the winding of the fourth auxiliary relay, a circuit including a front contact of said fourth auxiliary relay for supplying periodically interrupted energy to the rails of said rearward section, a signal controlling trafiic in said forward section, a circuit including a back contact of said fourth auxiliary relay for conditioning said signal to display its most restrictive indication, and a circuit including a front contact of said fourth auxiliary relay for conditioning said signal to display a less restrictive indi- 20 cation.

LESLIE R. ALLISON. 

